Practical application of new synthetic molecules for the betterment of human health depends directly on the efficiency with which these compounds can be synthesized, but this is frequently limited by poor reaction yields throughout long reaction sequences in which intermediate compounds must be isolated and purified. Metabolic engineers have demonstrated that novel biosynthetic pathways can be assembled in order to produce chemicals in vivo with no isolation of intermediates in an aqueous aerobic environment, but these sequences are limited to transformations catalyzed by natural enzymes. This proposal describes the design, preparation, and application of a new class of artificial metalloenzymes that combines the scope of chemical catalysis with the efficiency of biosynthesis in an unprecedented manner to produce molecules of exceptional biological importance. The proposed system offers a number of significant advantages over previous artificial metalloenzyme constructs, which enable its use for in vivo catalysis and metabolic engineering. This ambitious project will be conducted as part of the candidate's long term goals of increasing the efficiency of organic synthesis, particularly for the production of biologically active molecules. In the mentored phase (K99) of the proposed research, amino acids with catalytically active palladacycle side chains will be synthesized, characterized, and incorporated into a suitable scaffold protein. The catalytic activity of the resulting metalloenzymes will be evaluated using a variety of C-C bond forming reactions. The proposed amino acids catalysts could prove highly useful for a variety of applications in their own right, and their incorporation into proteins would mark a significant achievement in the fields of UAA incorporation and biocatalysis with potential applications well beyond the scope of this application. This research will be conducted in the laboratory of Professor Frances Arnold, a leader in the field of protein engineering, at the California Institute of Technology, a world-renowned research institution. Professor Arnold has a strong record as a mentor of successful members of industry and academia, and she and the candidate have outlined a career development plan focusing on mentorship, writing, and research to ensure the candidate continues this trend. The facilities, faculty, and staff at Caltech are ideal for completion of the proposed research and will contribute greatly to the candidate's overall development as an independent scientist. Independent (R00) research will focus on directed evolution of artificial metalloenzymes for in vivo palladium catalysis of pharmaceutically important cross-coupling reactions with potential applications in organic synthesis and bio-orthogonal diagnostics. Optimized metalloenzymes will also be expressed with additional enzymes in E. coli in order to biosynthesize biologically active molecules, including indolocarbazole natural product derivatives. Success in this venture would greatly expand the scope of molecules available via metabolic engineering and simplify the production of new compounds for the betterment of human health. This work will build directly on the candidate's experiences in the Arnold lab, and should foster the development of an exciting and collaborative research environment in the candidate's independent laboratory focusing on the development and application of enzymes for sustainable organic synthesis.